1. An exclamation of superiority2. Phrase exclaimed when the opposite team/opponent is pwned or defeated.
3. Phrase taken from Zero Wing, a poorly translated Japanese-to-English video game, in which the character Cats exclaims.

Stan means you look up to that person, you watch them or you truly love their content. It's another word for saying you idolize someone or something. You would say, "I stan_____" instead of I "I love that person"